The HIV scare comes less than one month after the launch of a new online sexual health database aimed at preventing the spread of sexually transmitted diseases among porn actors through mandatory testing. To be listed in the database -- a requisite for getting work -- porn actors must get tested every 30 days and present a clean bill of health. But critics say routine testing does not prevent STDs from creeping in.

"Testing is not a substitute for condom use, and it never will be," said Michael Weinstein, president of the AIDS Healthcare Foundation in Los Angeles. "No test can detect HIV from the moment of infection. There will always be a window period," which might not reflect recent infection.

The Free Speech Coalition, the industry trade group behind the database, announced the positive HIV test and requested the voluntary production moratorium Monday. A spokeswoman did not immediately respond to ABC News’ request for comment.

The positive test results will be confirmed by more sensitive testing methods, but details of the case, including the performer's name, age and sex, will not be released. It is also unclear how many sexual partners might be at risk.

"The average American male has seven female sexual partners in a lifetime. But it's possible for a male to have seven sexual partners in a single day on porn movie set," said Weinstein. "Because this is a network that's kind of inbred, the spread of disease could be exponential."

The AIDS Healthcare Foundation is pushing for mandatory condom use in the making of adult films -- a move that's met with strong resistance from the industry itself.

The online database, launched Aug. 2, lists pornography performers who are free of sexually transmitted diseases and available for work. It replaced an earlier version operated by AIM Medical Associates that was shut down in May after the site was hacked and performers' private medical information was leaked online. It's unclear whether a lapse in STD testing between May and August contributed to the new case.

The AIDS Healthcare Foundation is lobbying for a measure on L.A.'s June 2012 ballot that would mandate condom use in porn productions that seek city film permits.

"This is a tragedy, and we don't want to see one more person become infected with HIV or any other disease," Weinstein said.